/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
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/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#ifndef	_CRCMODEL_H
#define	_CRCMODEL_H

#include <sys/types.h>

#ifdef __cplusplus
extern "C" {
#endif

/*
 *
 *                             Start of crcmodel.h
 *
 *
 * Author : Ross Williams (ross@guest.adelaide.edu.au.).
 * Date   : 3 June 1993.
 * Status : Public domain.
 *
 * Description : This is the header (.h) file for the reference
 * implementation of the Rocksoft^tm Model CRC Algorithm. For more
 * information on the Rocksoft^tm Model CRC Algorithm, see the document
 * titled "A Painless Guide to CRC Error Detection Algorithms" by Ross
 * Williams (ross@guest.adelaide.edu.au.). This document is likely to be in
 * "ftp.adelaide.edu.au/pub/rocksoft".
 *
 * Note: Rocksoft is a trademark of Rocksoft Pty Ltd, Adelaide, Australia.
 *
 *
 *
 * How to Use This Package
 * -----------------------
 * Step 1: Declare a variable of type cm_t. Declare another variable
 *         (p_cm say) of type p_cm_t and initialize it to point to the first
 *         variable (e.g. p_cm_t p_cm = &cm_t).
 *
 * Step 2: Assign values to the parameter fields of the structure.
 *         If you don't know what to assign, see the document cited earlier.
 *         For example:
 *            p_cm->cm_width = 16;
 *            p_cm->cm_poly  = 0x8005L;
 *            p_cm->cm_init  = 0L;
 *            p_cm->cm_refin = TRUE;
 *            p_cm->cm_refot = TRUE;
 *            p_cm->cm_xorot = 0L;
 *         Note: Poly is specified without its top bit (18005 becomes 8005).
 *         Note: Width is one bit less than the raw poly width.
 *
 * Step 3: Initialize the instance with a call cm_ini(p_cm);
 *
 * Step 4: Process zero or more message bytes by placing zero or more
 *         successive calls to cm_nxt. Example: cm_nxt(p_cm,ch);
 *
 * Step 5: Extract the CRC value at any time by calling crc = cm_crc(p_cm);
 *         If the CRC is a 16-bit value, it will be in the bottom 16 bits.
 *
 *
 *
 * Design Notes
 * ------------
 * PORTABILITY: This package has been coded very conservatively so that
 * it will run on as many machines as possible. For example, all external
 * identifiers have been restricted to 6 characters and all internal ones to
 * 8 characters. The prefix cm (for Crc Model) is used as an attempt to avoid
 * namespace collisions. This package is endian independent.
 *
 * EFFICIENCY: This package (and its interface) is not designed for
 * speed. The purpose of this package is to act as a well-defined reference
 * model for the specification of CRC algorithms. If you want speed, cook up
 * a specific table-driven implementation as described in the document cited
 * above. This package is designed for validation only; if you have found or
 * implemented a CRC algorithm and wish to describe it as a set of parameters
 * to the Rocksoft^tm Model CRC Algorithm, your CRC algorithm implementation
 * should behave identically to this package under those parameters.
 *
 */


/* The following definitions are extracted from my style header file which */
/* would be cumbersome to distribute with this package. The DONE_STYLE is the */
/* idempotence symbol used in my style header file. */

#ifndef DONE_STYLE

typedef unsigned bool;
typedef unsigned char *p_ubyte_;

#ifndef TRUE
#define	FALSE 0
#define	TRUE  1
#endif

/* Change to the second definition if you don't have prototypes. */
#define	P_(A) A
/* #define P_(A) () */

/* Uncomment this definition if you don't have void. */
/* typedef int void; */

#endif

/* CRC Model Abstract Type */
/* ----------------------- */
/* The following type stores the context of an executing instance of the */
/* model algorithm. Most of the fields are model parameters which must be */
/* set before the first initializing call to cm_ini. */
typedef struct
{
	int cm_width; /* Parameter: Width in bits [8,32]. */
	uint32_t cm_poly; /* Parameter: The algorithm's polynomial. */
	uint32_t cm_init; /* Parameter: Initial register value. */
	bool cm_refin; /* Parameter: Reflect input bytes? */
	bool cm_refot; /* Parameter: Reflect output CRC? */
	uint32_t cm_xorot; /* Parameter: XOR this to output CRC. */

	uint32_t cm_reg; /* Context: Context during execution. */
} cm_t;
typedef cm_t *p_cm_t;

/* Functions That Implement The Model */
/* ---------------------------------- */
/* The following functions animate the cm_t abstraction. */

void cm_ini P_((p_cm_t p_cm));
/* Initializes the argument CRC model instance. */
/* All parameter fields must be set before calling this. */

void cm_nxt P_((p_cm_t p_cm, int ch));
/* Processes a single message byte [0,255]. */

void cm_blk P_((p_cm_t p_cm, p_ubyte_ blk_adr, uint32_t blk_len));
/* Processes a block of message bytes. */

uint32_t cm_crc P_((p_cm_t p_cm));
/* Returns the CRC value for the message bytes processed so far. */

/* Functions For Table Calculation */
/* ------------------------------- */
/* The following function can be used to calculate a CRC lookup table. */
/* It can also be used at run-time to create or check static tables. */

uint32_t cm_tab P_((p_cm_t p_cm, int index));
/* Returns the i'th entry for the lookup table for the specified algorithm. */
/* The function examines the fields cm_width, cm_poly, cm_refin, and the */
/* argument table index in the range [0,255] and returns the table entry in */
/* the bottom cm_width bytes of the return value. */

#ifdef __cplusplus
}
#endif

#endif /* _CRCMODEL_H */
